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Changes in gene expression before, during and after five generations of permethrin laboratory selection were monitored in six strains of Aedes aegypti: five F2- F3 collections from the Yucatán Peninsula of Mexico and one F2 from Iquitos, Peru. Three biological replicate lines were generated for each strain. The response to selection was measured as changes in the lethal and knockdown permethrin concentrations (LC50, KC50) and in the frequency of the Ile1,016 substitution in the voltage-gated sodium channel ( para) gene. Changes in expression of 290 metabolic detoxification genes were measured using the ' Aedes Detox' microarray. Selection simultaneously increased the LC50, KC50 and Ile1,016 frequency. There was an inverse relationship between Ile1,016 frequency and the numbers of differentially transcribed genes. The Iquitos strain lacked the Ile1,016 allele and 51 genes were differentially transcribed after selection as compared with 10-18 genes in the Mexican strains. Very few of the same genes were differentially transcribed among field strains but 10 cytochrome P450 genes were upregulated in more than one strain. Laboratory adaptation to permethrin in Ae. aegypti is genetically complex and largely conditioned by geographic origin and pre-existing target site insensitivity in the para gene. The lack of uniformity in the genes that responded to artificial selection as well as differences in the direction of their responses challenges the assumption that one or a few genes control permethrin metabolic resistance. Attempts to identify one or a few metabolic genes that are predictably associated with permethrin adaptation may be futile. [ABSTRACT FROM AUTHOR]

Chromosomal inversions are prevalent in mosquito species but polytene chromosomes are difficult to prepare and visualize in members of the tribe Aedinii and thus there exists only indirect evidence of inversions. We constructed an F1 intercross family using a P1 female from a laboratory strain of Aedes aegypti aegypti ( Aaa) and a P1 male Aedes aegypti formosus ( Aaf) from a strain collected from south-eastern Senegal. Recombination rates in the F2 offspring were severely reduced and genotype ratios suggested a deleterious recessive allele on chromosome 3. The F2 linkage map was incongruent in most respects with the established map for Aaa. Furthermore, no increased recombination was detected in F5 offspring. Recombination rates and gene order were consistent with the presence in Aaf of at least four large inversions on chromosome 1, a single small inversion on chromosome 2 and three inversions on chromosome 3. [ABSTRACT FROM AUTHOR]

Genome sizes and the organization of repetitive DNA were determined in the hard ticksIxodes scapularisandBoophilus microplususing reassociation kinetics. TheI. scapularisgenome contains∼2.15 pg (2.1 × 103 Mbp) of DNA and consists of no foldback (FB), 27% highly repetitive (HR), 39% moderately repetitive (MR), and 34% unique DNA. TheB. microplusgenome contains 7.5 pg (7.1 × 103 Mbp) DNA, and consists of 0.82% FB, 31% HR, 38% MR, and 30% unique DNA. In both species, repetitive sequences occur in a mixture of long and short period interspersion but most (65–80%) of the DNA follows a pattern of short period interspersion. Genome size and organization in the three tick species so far examined are distinct from other arthropods in having a greater proportion of MR, a lower proportion of unique and HR DNA of very low sequence complexity. [ABSTRACT FROM AUTHOR]

Abstract Plasmid libraries enriched for microsatellites were generated in the tick, Ixodes scapularis and in the mosquito Aedes aegypti. Libraries were enriched for genomic DNA containing (AC)n, (AG)n, (ATG)n, (CAG)n, (TAG)n, (AAT)n, (CTGY)n or (GATA)n motifs. Clones containing each motif were sequenced in both species for PCR primer design. In I. scapularis, most primers amplified a single locus and alleles varied in the number of microsatellite repeats and segregated as codominant markers. In contrast (AC)n, (TAG)n and (GATA)n microsatellite loci extracted from Ae. aegypti appeared to be members of multigene families. A primer pair designed to amplify a particular TAG locus instead amplified many independently segregating loci, some of which did not contain TAG microsatellites. Alleles at the TAG loci segregated as dominant markers and there was limited evidence for length variation among alleles. These results suggest that microsatellite loci are not universally abundant in arthropod genomes nor do alleles always segregate as codominant markers. [ABSTRACT FROM AUTHOR]